Health affecting, loss-inducing or otherwise harmful fungal pathogens (molds) pose a serious challenge in
many areas of human activities. On the contrary, frequent use of synthetic fungicides is undesirable in
some cases and may be equally problematic. Moreover, the ever more increasing fungal resistance
against commercial synthetic fungicides justifies development of rising efforts to seek new effective,
while environmentally friendly alternatives. Botanical fungicides based on Essential oils (EOs) undoubtedly
provide such an alternative. The study explores the efficacy of 20 EOs against Alternaria alternata,
Stachybotrys chartarum, Cladosporium cladosporioides and Aspergillus niger, related to abundance of majority
active substances. Minimum inhibitory concentration (MIC100 and MIC50) was evaluated. GC–MS analysis
revealed high abundance of highly effective phenolic compounds whose different molecular
structures correlates with differences in EOs efficacy. The efficacy of some EOs, observed in our study,
can be similar to the levels of some synthetic fungicides used in medicine and agriculture e.g. sometimes
problematic azole-based formulations. Thanks to the EOs environmental safety and natural origin, they
offer the potential to become an alternative where the use of synthetic fungicides is impossible for various
reasons.